The present invention finds particular application in association with welding, and especially with automated welding systems, and will be described with particular reference thereto. It is to be appreciated, however, that the invention is equally applicable for use in association with numerous other automated systems or in any other suitable manner. For example, the present invention can be used in association with painting and/or other automated coating systems.
Robotic positioners have been provided heretofore and generally include, as shown in Caldarone, for example, two or more workpiece support platforms, each rotatable between a load/unload position and a working position. The working position might be adjacent a welding head for performing a welding operation, for example. Typically, a robotic positioner also includes one or more shields or guards extending along the positioner between the support platforms in the load/unload position and the working position. In many cases, the support platforms themselves are rotatable so that the workpiece being processed can be rotated while in the working position, for example. Additionally, it is often desirable to support the workpiece at an angle relative to horizontal while in the working position. As an example, it is desirable to have a welding head positioned so that the welding operation is generally vertical. This is normally referred to as down welding and is a process that can be used to produce high-quality weld joints if the geometry of the workpiece is properly oriented relative to the welding head. As such, robotic positioners commonly extend a support platform at an angle, such as 45 degrees, for example, relative to horizontal, when such a support platform is in the working position. Thus, in this example, the surfaces to be welded might extend at an angle of 90 degrees relative to one another and at 45 degrees relative to the welding head, permitting a high-quality weld joint to be formed as a result of the down weld operation.
Certain disadvantages exist, however, in known robotic positioners, such as Caldarone, for example. One disadvantage is that a support platform in the load/unload position is generally not horizontal when another support platform is in the working position and is properly oriented relative to a welding head, as discussed above, for example. It will be appreciated that workpieces are commonly fed to and taken away from a workstation by generally horizontal conveyors. As such, the workpieces thereon are likewise in a generally horizontal orientation. As a result, the loading and unloading of a workpiece on a non-horizontal support platform, such as is shown in Caldarone, for example, can be difficult and undesirably requires manual manipulation of the workpiece to properly orient and secure the same to the non-horizontal support platform. The same disadvantage exists when removing a processed workpiece from a support platform in the load/unload position as the processed workpiece generally must be reoriented, that is rotated or turned, into a suitable position to engage the generally horizontal conveyor.
Other robotic positioners are known that have just a single support platform supported on a base structure. The support platform typically includes two axes, one of which is a generally horizontal axis and the other a central axis extending generally transverse to the horizontal axis. The support platform is adapted to tilt about the horizontal axis and is rotatable about the central axis. However, since the robotic positioner has only one support platform, two or more robotic positioners are commonly used together at one time to form a work cell. One disadvantage of such arrangements is that the operator is required to walk back and forth between the two positioners to load or unload one workpiece while another workpiece is being processed on the other positioner. Another disadvantage of such arrangements is that the two robotic positioners have a total of four axes, and, therefore, also include at least four actuators for effecting rotation about these axes, as well as a control system for coordinating and controlling the operation of the two positioners. As such, these systems are complex and expensive to produce and maintain. Adding further to the expense is that safety equipment, such as shields and guards, for example, are required for both positioners. So, the cost of purchasing and maintaining such safety equipment can be significantly more expensive than that for only one positioner. Still another disadvantage is that the two machines can take up considerable floor space, which is a significant disadvantage in facilities where floor space is otherwise limited.
Still other robotic positioners are known that rotate two or more support platforms about a vertical axis rather than a horizontal axis, such as is shown in Caldarone, for example. Because such other robotic positioners rotate about a vertical axis, the positioners can either have two or more generally horizontal support platforms, two or more inclined support platforms, or two or more support platforms that each have a horizontal axis permitting selective pivoting or tilting of the support platform between horizontal and inclined orientations. Either of the two former configurations undesirably restrict the support platforms to either a respective horizontal working position or an inclined load/unload position, whereas the latter of the three positioners is configured such that each support platform has a horizontal axis that permits both a horizontal load/unload position and an inclined working position. This configuration, too, however, has disadvantages. One such disadvantage is that this robotic positioner has an additional axis for each support platform. As a result, this robotic positioner can have five or more axes, including one (1) central vertical axis, two (2) vertical platform axes, and at least two (2) horizontal axes for pivoting or tilting of the two platforms between horizontal and inclined orientations. This significantly increases the cost, size and overall complexity of both the robotic positioner, as well as the attendant control system therefor.